D5 185 with a very odd problem

[Horton]

I thought I'd post this up as a recent experience in our workshop that I've never seen before!
A couple of weeks ago, a local chap pitched up with a gnarly old 185 brake 2006 xc90. He was complaining of the usual gear change issues, and admitted he had just bought it from the auctions. I drove it, and advised him to get the valve body changed to cure the jerky gearbox, and he booked it in for the work to be done the next Monday.
Well... When he arrived, he also mentioned it was puffing out loads of smoke at random intervals and could we look at this. I took it for a drive, sat at some traffic lights and pulled away.... It smoked like a trooper and I decided it needed a closer look before going any further. My first thought was turbo or valve stem seals. VIDA came up with weak turbo pressure but little else, so I started to thinking it might be turbo. I took it again for another test drive along one of my favourite routes and eventually found that the car smoked when I went round a left hand bend!???
Back at the workshop, and with the car in the air it was apparent someone else had decided the turbo was faulty as there was a new one fitted! I phoned the owner to ask if he had any history, but sadly there was nothing. We then phoned the garage who's name was on the number plates and discovered a tale of woe. Previous owner had thrown thousands at it trying to get to the bottom of the issue, to no avail, and given up by chucking it at the auctions....
It was obvious the issue was internal and we advised the owner to replace the engine on the basis this would be cheaper than stripping it down to find out what was wrong, and then repairing it! Extreme, but we had a nice low mileage one that was available at a good price and it worked out cheaper.
So, that was all done, gearbox fixed, and a rather large bill reflecting what he should have paid for the car in first place! It's now lovely.
Well, rather than dump the engine, we decided to strip it down, and took the head off. There were no obvious issues and everything seemed OK. Stumped I sent the head off to be tested and my engine machinist found the issue....... Two valve guides were broken, snapped where the stem seal fitted to the top of the guide so the seal randomly moved up and down as the valve moved, sometimes sealing, other times not😳
Never, ever seen this before, I'll try and post some pics so you can see what happened, but I thought it would be useful for others in case someone has similar symptoms.